Pair study effect of acidity, warm water on Dungeness crab

Juvenile Dungeness crabs are about to become lab rats for Aaron Galloway and Julie Schram of the Oregon Institute of Marine Biology in Charleston.

And with a lot of work and a little luck, the two researchers might be able to help the crab fishery — if needed — in the face of warming water and increasing acidity in the ocean.

Galloway gave a presentation last week in Harbor for the Oregon Dungeness Crab Commission in which he outlined the research he and Scham, an ocean acidification expert, plan to conduct under an Oregon Sea Grant they were awarded this week.

The research could help determine how — and if — the crab fishery is in danger.

“The crabbing industry in Oregon is the most valuable single-species fishery — most years,” said Hugh Link, director of the Oregon Crab Commission. Oregon brought in 20,447,986 pounds crab this last season, of which 2,131,369 pounds were harvested from the Port of Brookings Harbor.

The value of those crab — just to fishermen — represented $6.42 million here, of $62.8 million statewide. Oregon fishermen harvested $128 million for all fisheries combined.

Some years, Link said, Brookings has brought in more crab than any other port in the state, including Astoria, Newport and Coos Bay.

The study

Galloway and Schram plan to study over the next two years if Dungeness crabs are even affected by increasing carbon dioxide levels in the ocean that result in an increase in acidity, or pH, in that water.

Research on bivalves — hard-shelled mollusks, such as clams, oysters and mussels — has shown that increased acidity in the water makes it difficult to build shells. But very little research has been conducted on crabs, whose shells aren’t as hard.

“It’s pretty well-known that shell-forming bivalves can have some serious challenges,” said Galloway, a former fisherman from Juneau, Alaska. “I’m excited about Dungeness crabs because they’re such an important part of our economy. I’m interested in long-term, sustainable fisheries, and the Dungeness crab is a really good fishery in that regard. It’s in really good shape.“

Their studies might not result in anything. At the minimum, they will provide more information to the growing cache for researchers as they try to figure out how climate change is affecting the Earth and its biosphere.

The ocean and pH

The ocean is the world’s biggest absorber of carbon dioxide, and its increase has resulted in increased acidity levels of the water. In the past 200 years, the acidity of the ocean has increased 0.1 pH units. That scale, like the Richter scale, is logarithmic, so this change represents approximately a 30 percent increase in acidity.

Warmer ocean waters and pH changes have also resulted in great die-offs of reefs, including the Great Barrier Reef in Australia, parts of which are in complete collapse.

But crabs can’t be compared with reefs or mussels — and theories are meant to be proven, refined or destroyed.

Schram, who studied ocean acidification in Antarctica where cold water absorbs carbon dioxide more rapidly, said she was surprised by some of the results of her doctoral work there.

“Some species I thought would be really sensitive were really tolerant, and some I thought would be really tolerant were really sensitive,” she said. “It made me look closer at a lot of my assumptions.

“Two other species … I figured they’d be fine, but both — I could not keep them alive at a low pH,” she said. “And it got worse with elevated temperatures. I understand why previous researchers thought (what they did).”

Conversely, snail and limpids, both of which feature thin, fragile shells, were thought to be extremely susceptible to lower pH levels.

“They ended up not being affected at all,” Schram said. “Maybe it’s because they’re very long-lived, and over a lifetime can adapt. The underlying thing is their assumption. I want to know if it’s true.”

The Pacific Ocean is unique in that it has natural upwellings of water that bring surges of cold water from the bottom of the ocean, providing food to those in shallow depths and mixing up the warm and cold waters critical for life. The researchers plan to use past research on upwelling to see how that unique phenomena affects Dungeness crab, as well.

“In areas where there aren’t as much variations in ocean upwelling, there might be some species that are not used to the conditions we have here,” Galloway said. “Ours might be fine, while others might not. It’s not just that ocean acidification is unnatural or human-caused, but we want to understand what’s happening with organisms when we subject them to these conditions.”

Bitty crabs

No one has really studied juvenile crabs, either, Galloway and Schram said.

At the beginning of their lives, tiny Dungeness crabs float around with the plankton in the sea, later falling to the ocean floor to grow. And grow, they do, shedding shells over and over until they reach adulthood.

“That part, when they’re settling into the bottom, there’s not as much knowledge — even the biology is hard to study,” Galloway said. “They’re little and subtidal. We know a lot about crabs when we want to harvest them, when they’re four or five years old …”

Other research has hinted that ocean acidification might disorient crabs — an important theory yet to be proven. Crabs find prey — and avoid becoming prey — by sensing their environment, and if a crab can’t find the bait in the crab pot, that could spell fewer dollars in that fisherman’s wallet.

Schram and Galloway plan to study that, as well, he said.

Next spring, they’ll plumb the depths of the sea and bring the little crabs to their lab, subject them to varying pH levels of ocean water and see how they respond. Or not.

“Ocean acidification is somewhat unpredictable in how an organism might respond to it,” Schram said. “There are a lot of possibilities and not a lot known about it.”

“In talking with the general public, I always found that very difficult,” she said. “‘Antarctica; it’s so far away.’ We’re trying to get at the mechanisms, what species are going to be affected? If it’s ones we care about, should we know early on? It gives us more time to figure out if we can help them. Or if not, ‘We’ll keep an eye on you, but see if there are other species we need to focus on.’”

Galloway and Schram emphasized they’re merely trying to see how the environment affects a species so critical to coastal economies.

“I”m trying to figure out what the message is,” Galloway said. “I don’t have an agenda, I really don’t care if ocean acidification doesn’t affect crabs. I don’t want to get into global warming; the fact is, this is what we’ve got. And it looks like it’s going to continue. I’m just interested in it because we need to know.”

Schram agreed: “It is happening, regardless of what you think the triggers is, there are changes,” she said. “If it’s relevant to these critters in their lifetimes; it’s important to know if they need help, if the critters we care about are going to still be there. There’s going to be winners and losers; there always are when there’s a change. I think that gets missed.

“It’s not doom and gloom, either; I’m hopeful,” she added. “This is a really young field. We’re learning a lot, but we don’t have the whole picture yet.”